(a) Field of the Invention
The present invention relates to a chip antenna, and more particularly, to a ceramic chip antenna capable of utilizing a plurality of bands since spirally wound conductors operating at each other different frequencies is formed within the ceramic chip.
(b) Description of the Prior Arts
FIG. 1A is a representation of a conventional dipole antenna. As shown in FIG. 1A, a conventional dipole antenna includes two-quarter wavelength dipoles 1 and 3. The dipole antenna was quite acceptable as antennas for low frequency fixed station transceivers. The dipole antenna has the advantage of a relatively large bandwidth. However, with the advent of portable transceivers operating at relatively high frequencies, the large size of the dipole antenna with respect to the relatively small size of the portable transceiver makes such dipole antenna impractically large for employment on such a transceiver. Unfortunately, the size of the dipole antenna is too large to be aesthetically acceptable with respect to the modern relatively small portable transceivers.
FIG. 1B is a side view of a conventional helical antenna. As shown in FIG. 1B, a conventional helical antenna includes a cylindrical support member 5. The support member 5 is composed of an electrically insulative material. A conductor 7 is spirally wound around the portion of the support member 5. Here, a resonating frequency is determined by the number of turnings, the interval of turnings, and the length of the conductor 7. Since the size of the helical antenna is relatively small, the helical antenna is acceptable with respect to the small portable transceivers. However, the helical antenna operating at single band is not suitable for a portable transceiver operating at two bands.
FIG. 1C is a side view of a conventional dual band helical antenna. As shown in FIG. 1C, a conventional dual band helical antenna includes a cylindrical support member 9. The support member 9 is comprised of an electrically insulative material. A conductor 15 of electrically conductive material is spirally wound around the upper portion 11 of the support member 9. A conductor 17 of electrically conductive material is spirally wound around the lower portion 13 of the support member 9. Accordingly, the dual band helical antenna is suitable for a transceiver operating at two bands.
Typically, a helical antenna is retractably formed on the top plane of a portable transceiver. Then, a user uses the portable transceiver after drawing out the helical antenna from the transceiver and keeps the transceiver after putting the helical antenna in the transceiver. Since the helical antenna is projected from the top plane of the transceiver, the helical antenna is easy to break and is unhandy to carry about. Also, the relatively large size of the helical antenna makes difficult to get smaller with respect to the size of the portable transceiver.
One solution to the above antenna problem is to form a chip antenna inside of a portable transceiver. The chip antenna is manufactured by utilizing a ceramic chip manufacturing technology.
FIG. 2 is a perspective view of a conventional ceramic chip antenna. As shown in FIG. 2, a conventional ceramic chip antenna has a ceramic chip 19 formed as a rectangular parallelepiped and a conductor which is spirally wound inside the ceramic chip 19. The conductor includes horizontal strip patterns 21 which is formed by printing and is parallel to a mounting surface 25 of the ceramic chip 19, and perpendicular strip patterns 23 formed by filling via holes being perpendicular to the mounting surface 25 with electrically conductive paste. Further, one end of the conductor is led to an outside surface of the ceramic chip 19 to form a feeding terminal for applying a signal to the conductor. FIG. 3 is a return loss vs. frequency graph of the ceramic chip antenna. Such graph shows a rather sharp peak in return power loss at predetermined frequency fo and thus the ceramic chip antenna is usable for operating in only a relatively narrow bandwidth centered around the frequency fo.
However, the ceramic chip antenna would not be suitable for a portable transceiver operating at two bands or more.